COPFAS

In 2007, over 8,500 properties were affected by flooding in Hull City. The flooding saw numerous main roads through Willerby, Derringham, Cottingham, and Orchard Park become rivers without any alternative natural water course.  

In a unique position, the city of Hull is settled on flat land adjacent to the sea and close to sea level, with several surrounding valleys that drain their rainwater into the basin in which Hull city centre sits.

The disaster affected other regions as well as Hull, leading to a partnership between East Riding of Yorkshire Council and Hull City Council. Additionally, this also led to the support from the Environment Agency, and Humber Local Enterprise Partnership as a joint venture to find solutions to reduce the threat of repeat flooding.

The Cottingham and Orchard Park Flood Alleviation Scheme (COPFAS) is the second project undertaken through the Hull City Council and East Riding of Yorkshire Council partnership. The scheme protects 4,000 properties in Cottingham and Hull's Orchard Park from future flooding.

The COPFAS hydraulic model has been adapted from the earlier River Hull Integrated Catchment Model and trimmed down into a smaller single catchment area model. Through the model analysis, the COPFAS proposals included the creation of nine reservoirs for rainwater storage along Eppleworth and Westfield Road, and another reservoir adjacent to North Moor Lane, Cottingham.  These reservoirs will resemble grazing areas or be used as arable fields and remain as dry land ready to be filled during severe wet weather events.  The reservoirs are large raised reservoirs under the Reservoirs Act and as such are being constructed under the supervision of Pell Frischmann’s Reservoir Construction Engineer.

Careful attention needed to be paid to lining the reservoirs to prevent pollution of the underlying chalk aquifer which supplies drinking water to Hull and the surrounding area.  Extensive geotechnical testing and negotiations with the Environment Agency and Yorkshire Water has enabled the reuse of existing clay on the sites to line the reservoir and build embankments thereby saving our client millions of pounds.

For flood waters to reach the reservoir near Orchard Park, our engineers designed a new channel to connect two existing culverts underneath a nearby railway line.  Refurbishing these culverts instead of building a new, larger culvert under the railway allowed our client to save over a million pounds.

With planning permission granted and detailed design complete, the first reservoirs is being built and expected to be completed in the summer of 2018 with the remaining nine reservoirs completed in late 2019.

Both the Willerby and Derringham, and Cottingham and Orchard Park flood alleviation schemes will enable the great protection of residents, their homes, and businesses within the area. Pell Frischmann have been able to deliver sufficient benefits with minimum cost, aiding COPFAS to provide protection for up to a 1 in 75-year flood event with an allowance for future climate change.

Stats

  • icon-arrow10 - reservoirs created storing over 330,000 m3 of flood water
  • icon-arrow4,000 - properties protected
  • icon-arrow1 in 75 - year flood event plus climate change allowance

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